1. Field of the Invention
The present invention relates to a plastic lead frame and the fabrication method of same, in particular, to a plastic lead frame with high reflection efficiency, enlarged conductive area and high heat conductivity, and its simple and low cost fabrication process.
2. Description of the Prior Art
Usually, the LED lead frame is normally made of conductive sheet materials such as copper, copper alloy or aluminum by punch process to form a basic material of the lead frame, afterwards the surface of the basic material is electroplated to form a layer of high conductive metal using Sn, Ag or Au, finally it is formed into a cup shaped LED lead frame by the process of insert molding. However, it is regretful that the reflection area of the cup shaped lead frame fabricated as such fails to provide an effective reflection with its metal layer.
Alternatively, process of Laser Direct Structuring (LDS) can be applied to the fabrication of the LED lead frame, but it is disadvantageous that the specially designated material is needed to carry out this process so as to activate the surface of the electrodes and the reflection area with laser beams, by so, the surface thereof is granulated by laser, and the area to be radiated by laser is too large, the tilted surface of the conductor frame work receives less laser beams, and the time is limited to carry out the process, all these factors added to result in a deviation of the actual refection direction and the reflection luminance from the originally expected value. Besides, to run 3 dimensional laser machining equipment is quite expensive, it requires too long operation time, so that the production cost will be excessively high.
Another selection is the low temperature co-fired ceramics (LTCC). As the ceramic resembles with silicon in its property so that it can be connected with an electronic chip, it has a high heat conductivity and high refractory property. However, the LTCC process is carried out with a temperature of about 900° C. which brings about a non-uniform shrinking causing variation in electric property of the product. Besides, it is expensive to carry out LTCC process that causes the difficulty for mass production with a reduced cost.
There are manufactures that have intended to fabricate the lead frame by applying two-shot molding technique. Presently there are two selections, namely PCK and SKW. In PCK process, the plastic material which being electroplated and modified by the catalyst is employed at first time, then a non-electroplating plastic is employed in second time, after that the surface of the work piece is activated by etching and metalizing. As for SKW process, an electroplatable plastic material is used in molding at first time, then followed by etching the surface of the plastic material formed in the preceding process, and activating the surface thereof with Pd. Afterwards the work piece is placed in the mold for the second time molding and then metalizing the surface thereof. The aforesaid two methods are inappropriate to apply for machining a very fine and sophisticated wiring by reason that such a very fine and sophisticated wiring can not be effectively finished by employing two-shot molding technique.
In other words, presently the manufacturers have encountered difficulty in fabrication of the conventional complicated LED lead frame causing them unable to lower the production cost. The granulated surface resulted after the laser beam radiation is unable to acquire the desired reflection direction, luminance and efficiency, inapplicable to form an insulation route pattern with micromachining, all these flaws have to be solved. It is a paramount importance to develop a technique capable of fabricating a LED lead frame with the excellent characteristics such as high reflectivity and can be made easily with a low production cost for the benefit of both manufacturers and users.
In view of the foregoing situation, the inventor of the present invention herein has gone to great lengths by conducting an intensive research based on many years of experience gained through professional engagement in the manufacturing of related products, with continuous experimentation and improvement culminating in the development of the improved structure of the plastic lead frame with reflection and conduction metal layers, and the fabrication method thereof.